Mapping The Study Area

Transcription

1 While on the beach you will need to take some measurements to show where the study area is relative to the rest of the world and to show what is inside the study area. Once the measurements have been taken, you will be able to take a close look at the animals and plants in the study area. WHAT IS A SKETCH MAP? A sketch of the study area provides a detailed view of the study area. When complete it shows the general lay of the land, and where features and habitats are located. The sketch map you make today will be important when the survey is done again. The sketch map will be scanned and stored as a computer file along with the rest of the data collected. An example of a completed Form 4: Sketch Map form is included here (Figure 8). A blank Form 4: Sketch Map form is included in Appendix B. If the backshore is not on private property you can survey it and measure its width. You need only go back 20 m. If it is private property, you may not be able to map it properly, so sketch what features you can see from the beach. Major features of the study area that need to be mapped are: the borders of the study area; the borders of habitats; the border between the Intertidal Zone and the Backshore Zone; the water s edge at low tide on the day of mapping; permanent features and/or installed markers used to triangulate the baseline end points. RECORD YOUR SKETCH MAP MEASUREMENTS ON A ROUGH SKETCH MAP The following steps show you how to develop the map. First, do a very rough sketch with all the measurements at the beach. Once all the necessary measurements are made on the rough sketch, carry on with the rest of the survey. The final copy of the map drawn to scale on Form 4 can be done towards the end of your survey. 48

2 Figure 8. Example of a Completed Form 4. SHOREKEEPERS GUIDE - MODULE 1 APRIL

3 STEP 15: DESCRIBE THE LOCATION OF BASELINE END POINTS Where to Record Data FORM HEADING 1 Description and Locations of Permanent Triangulation Markers Location of Baseline End Points Relative to Above Markers 4 Sketch Map Materials Needed long measuring tape or surveyor s hip chain or rangefinder calculator flagging tape compass Steps 15 and 20 deal specifically with the location of the baseline. In Step 15 you are asked to locate both ends of the baseline relative to local features, say a large tree or rock. Later, Step 20 requires you to locate at least one of the ends of the baseline relative to the rest of the world. The accuracy required in Step 20 has to be good enough to lead a new Shorekeeper to the vicinity of the baseline end points, for example, we use longitude and latitude to locate the study area. The accuracy required in Step 15 is much greater. It has to be good enough to get that stranger within a half a metre or so of the end of the baseline. Record on Form 1 a description of each of the three or four permanent features or markers under Description and Locations of Permanent Triangulation Markers. Record where they are in relation to the baseline end point under Location of Baseline End Points Relative to Above Markers. Record on your sketch map the location of each end of the baseline (for each baseline you are using) in relation to two major landmarks, such as boulders or large trees in stable locations, dock pilings, the corners of buildings, or a permanent marker you install. This is called triangulation. Make sure these features are not too close together; they should be about 90 apart. You will have to use two different pairs of landmarks for each end of the baseline. The landmarks themselves may be quite big (for example, a wharf or a boulder). You have to specify exactly where on the landmark is the reference point (e.g. northeast fence post at base) when making measurements. 50

4 Alternatively, if it is difficult to see two prominent features for each end of a baseline, you can use one feature with a compass bearing and a single distance measurement. Record these on your rough sketch map or install permanent markers, see Step 16. On your rough sketch map draw in your baseline(s), the four permanent features, a description of them that allows another Shorekeeper to readily find them, and the distance from the end points to the permanent features. These measurements will allow you to use the same baseline next year. SHOREKEEPERS GUIDE - MODULE 1 APRIL

5 STEP 16: INSTALL PERMANENT BASELINE TRIANGULATION MARKERS (OPTIONAL) Where to Record Data FORM HEADING 1 Description and Location of Permanent Triangulation Markers Location of Baseline End Points Relative to the Above Markers Remember, it is important to get the consent of landowners, foreshore leasees, or First Nations before installing markers on their property. You should advise other local residents too, about your survey, so that if they find your survey markers while walking along the beach, they will not remove them or trip over them. If the study area has no suitable prominent features nearby with which to triangulate your end points, it may be necessary to install some permanent markers. You can do this at the end of the survey before you remove your baseline. To make a permanent marker, build a small cairn with cement and stones or fill a crevice with concrete, then install a roundheaded bolt, or some other length of steel that is not sharp. The bolt should be embedded in the cement with no more than 1 to 2 inches exposed for safety reasons. Your marker should be unobtrusive and placed above the high tide mark and preferably in the backshore. It should be somewhat sheltered from direct surf so that a big storm does not wash it away in the winter. Place the permanent marker as close as possible to prominent features that you can show on your sketch map. The permanent markers will help you or other survey teams to set up the same baseline next year. If possible, scratch in the DFO Shorekeepers Study Area number and the date before the cement dries. 52

6 STEP 17: MAP THE FEATURES OF THE STUDY AREA Mapping is very important and must be supervised by someone who has been trained in this task. Where to Record Data On your rough sketch map draw the following measurements as you make them, so as to keep track of your work. Backshore and Intertidal Zone: Draw the line showing the boundary between the intertidal zone and the backshore zone. Measure the distance perpendicular from the baseline to the landward end of the intertidal zone at regular intervals along the baseline. Measure your distance along the baseline relative to the 0 m mark. This task is made easier by the marked flagging tape woven into the baseline rope. Record these measurements on the rough sketch, showing the points on the baseline from which you measured, and the width measurements you made. For every measurement there should be two numbers: the point along the baseline in metres from the 0-m end; the perpendicular distance to the feature or habitat boundary. FORM HEADING Maximum Width of Study Area on the Survey Day Habitat Area GPS filename Sketch Map SHOREKEEPERS GUIDE - MODULE 1 APRIL

7 Major features: Follow the same procedure to map the major features in both zones. Using Differential GPS If you have a differential GPS, you can use it to more accurately map the boundaries of habitats in your study area. Record the GPS file name on Form 3 beside Habitat Area ea. Habitats: Habitat units are most often irregularly shaped. To map them you will need to take at least four or five sets of measurements to act as reference points around the edges of the unit (or more if the habitat is quite irregular). Then draw in the details as accurately as possible. Remember, the goal is to produce a reasonably accurate map of the habitat unit sizes, shapes, and locations within the study area, so that another Shorekeeper can accurately map a year to two later. Even if you have Differential GPS, you must still make a sketch map as a visual record. Record all the measurements on the rough sketch rather than just keeping a list of your measurements. The drawing will help to keep track of what measurements you have, and what measurements you still need to finish the sketch of the study area. Be sure to label all features and habitat units on the rough sketch. 54

8 Low tide mark: You need to take two more measurements the first of these is the width (the distance down to the water) of the study area at low tide on the day of the survey. You cannot get this measurement until the exact time of low tide. When the tide is at its lowest, make several width measurements at various points along the baseline to the low tide mark and record these on the rough sketch. Remember that the maximum width of the study area is the combined widths of the backshore and the intertidal zones at low tide on the day of mapping. The Backshore Zone: Your final measurement is the width of the backshore zone. From a work time perspective, it might be best to wait until the intertidal zone survey is complete before you actually make measurements. See Step 33. SHOREKEEPERS GUIDE - MODULE 1 APRIL

9 STEP 18: CALCULATE THE SCALE OF THE SKETCH MAP Where to Record Data FORM HEADING 4 Sketch Map The sketch map forms part of the data collected (it will be scanned into the central database by DFO), so it needs to be done as neatly and accurately as possible. This step describes how to calculate a proper scale for the sketch map. The scale will indicate how big objects are in real life. The sketch map should show the entire study area, even the backshore. The maximum width of the study area is the combined widths of both the backshore and the intertidal zone on the day of mapping. The length of the study area is the distance these zones extend along the shore inside the study area borders. Draw the sketch map on Form 4. This form has grid lines, 100 x 60. Each square will represent a certain distance on the beach. If your study area is 100 m by 60 m or less, you will be able to use a scale of 1 metre = 1 square. Try using this scale and see how it fits on Form 4. If the paper is too small in either or both directions, you will have to use a smaller scale. Try using a scale of 2 metres = 1 square. If the drawing fits on the paper, but it is very small and scrunched up, you will want to use a larger scale. Try using a scale of 1 metre = 2 squares. 56

10 Example: If the study area is 185 m long and 75 m wide, you would use a scale of 2 m = 1 square. The sketch map would then be 93 squares long (half of 185) and 38 squares wide (half of 75). Example: If the study area is 35 m long and 29 m wide, you would use a scale of 1 m = 2 squares. The sketch map would then be 70 squares long (two times 35) and 58 squares wide (two times 29). Remember to record the scale you are using on the map. If the study area is wider than it is long, then turn the paper lengthwise and use a scale that works. If you find this Step too difficult or confusing to complete properly, contact your DFO representative for assistance. Note: You have to use the same scale in both directions. SHOREKEEPERS GUIDE - MODULE 1 APRIL

11 STEP 19: REDRAW THE ROUGH SKETCH TO SCALE ON THE SKETCH MAP Where to Record Data FORM HEADING 4 Sketch Map Draw a thick line representing the baseline, then draw a line along the left side of the page, perpendicular to the baseline. Label the perpendicular line, this represents the Study Area Width. Each square is equal to the scale you calculated in Step 18 above. With the baseline being zero, label each square on either side of the baseline. Draw in the lines to show the back boundary of the backshore zone and the low tide line. Draw in the lines to show the two side boundaries of the study area. You are finished your sketch map when all the habitat boundaries and other features of your study area are mapped. Put a North arrow on the map using a compass or a published map of the area. Make sure it is oriented properly, and indicate whether your arrow represents Magnetic North or True North, see Step 21. Draw and label each feature and habitat unit. Write a one- or two-word label beside each feature you draw. Make sure the habitat units you map have the right location codes and correspond to the same habitat units described on Form 3. 58

12 STEP 20: TAKE BEARINGS FROM BASELINE END POINTS This Step, when combined with Step 21, will give accurate geographic coordinates for the study area. It actually gives coordinates for one of the end points of the baseline this point is the reference location point for the study area. This point is particularly useful if the study area is in a remote area where you cannot document the location relative to access roads. Along with the permanent features you have marked on the sketch map, this will make it easier to find the study area in the future. Two methods for estimating the location of the study area are outlined below. You can leave this step until the end of your survey, because it is not particularly constrained by the tide height, whereas mapping habitats and sampling quadrats are constrained. TAKING A COMPASS BEARING This section describes how to use a compass to triangulate and pinpoint your study area on a map or chart. Once you have marked the site on the map or chart of the area, it is a simple step to determine the coordinates of that position in the next step. CHOOSE AT LEAST TWO, PREFERABLY THREE, PROMINENT FEATURES Stand at one end of your baseline. Choose at least two, preferably three, large and obvious features that you can also find on your chart or topographic map. Points of land, lighthouses and other navigation markers are good if you are using a chart: buildings, heights of land, or radio towers are good if using a If you are using a GPS, then skip to Step 21 to determine the coordinates. Materials Needed compass with sighting mirror parallel ruler SHOREKEEPERS GUIDE - MODULE 1 APRIL

13 map. When choosing these features, keep the following points in mind: The nearer an object is to you, the more accurate the position of the bearing line. The three features should be approximately 90º apart from each other, if possible, for best accuracy. TAKE COMPASS BEARINGS Training and practice in this beforehand is a must! Hold your compass level with the mirror tilted so that you can read from the compass while still holding it horizontal at eye level. Line up the sighting notch with the object. Adjust the compass plate so that the north arrow (free moving red end) lies directly over the red arrow etched on the base of the compass. Now you can read the bearing off the compass. This is the magnetic bearing to the object. Write it on a piece of paper. Repeat this procedure for the other two features. 60

14 STEP 21: DETERMINE THE GEOGRAPHIC COORDINATES OF BASELINE END POINTS Plot your bearings on a hydrographic chart or topographic map that you chose in Step 7. Plot bearings on a hydrographic chart: Place your parallel ruler on the magnetic compass rose on the chart, and turn it so that the edge is along your compass bearing. Then work the parallel ruler across the chart until its edge is on the object. Draw a line from the object back towards shore. You were standing somewhere along this position line. Take your second bearing and do the same procedure to draw the bearing line on the chart. The point where the two bearing lines intersect should be your position. If you took a third bearing, plot this as well. It is unlikely that the three bearing lines will intersect at one point. It is more likely they will form a small triangle, with your position being somewhere in the triangle. If the triangle is large, or if the first two lines do not intersect, then you have made an error reading the bearing. Try again. Where to Record Data FORM HEADING 1 Estimated Baseline End Point Coordinates Source of Baseline Coordinates Plot bearings on a topographic map: Topographic maps use true north. So, on a topographical map you will have to change the magnetic reading from the compass into a true reading. True north is a fixed point at the north pole. Magnetic north is actually an area of magnetic fields deep inside the earth. The field is not located exactly at the north pole, rather it is about 2,092 km from true north and moves very slowly. A compass needle does not point to true north, it points to magnetic north. In British Columbia a compass needle points approximately 22º east of true north. To correct your compass readings to true north, you need to add 22º to the compass reading. See the topographic map for the exact correction (declination) to use. It should be recorded along the bottom margin. To plot your bearings, take your first bearing and add the declination. SHOREKEEPERS GUIDE - MODULE 1 APRIL

15 Example: Your magnetic bearing that you read from your compass is 180º. The declination you read off the bottom edge of the map is 22º. The corrected bearing from true north is 180º + 22º = 202º. Now, place your parallel ruler on the corrected bearing on the map s compass rose. Then follow the same instructions for the topographic map, using the corrected bearing as you would on the hydrographic chart (described above) to locate your baseline reference point. Repeat this procedure for your second and third bearings. Don t forget to add the declination to each bearing. You can determine your geographic coordinates later at home. If you used GPS in Step 20, then skip this. If you have trouble with any part of this step, an individual who has completed power squadron, or a forester, surveyor or geography teacher will be able to help you. It should only take a few minutes. Hydrographic Chart (Estimated Latitude/Longitude): Hydrographic charts have a grid on them representing latitude and longitude. Latitude is measured parallel to the equator in degrees, from 0º at the equator to 90º at the north pole. Longitude is measured at right angles to the equator starting at 0 near London, England, and going 180º east and 180º west. Latitude is read on the left and right sides of the chart. 1 minute of latitude equals about one nautical mile. Longitude is marked on the top and bottom of the chart. Lines of longitude converge at the north and south poles. As a result the distance between these lines varies with latitude. You cannot use longitude to measure distance. Each degree of latitude and longitude is further divided into 60 minutes, which is marked on the sides of the chart at oneminute intervals (01', 02', 03', etc.). Each minute block is further divided into 60 seconds. Seconds are spaced by dots into 10 equal parts, with each interval equalling 6 seconds (6", 12", 18", etc.). To estimate the coordinates of your location using a hydrographic chart, you will need to record a latitude value and 62

16 a longitude value for the reference point (one end of the baseline where you took your compass bearings) using the following procedures. The example used to illustrate the procedure is based on estimating the location of point 1 in Figure 9. Determine the latitude to the nearest second for the reference point: Read the nearest number of degrees given below the point, followed by the minute block the point is in. Example: If the point is in the 39 th minute block above 49º, its latitude to the nearest minute is 49º 39'. Determine the nearest second of the point, by measuring the ruler distance from the bottom of the nearest minute block to the point. Divide this value by the ruler distance for a minute of latitude. Example: If there are 84 mm in each minute of latitude, and the location is 60 mm above the minute line, then it is at = 0.72 minutes. Multiply this value by 60 to calculate the number of seconds. In the example given, 0.72 x 60 = 43.2 seconds. The final latitude would be written as Lat. 49º 39' 43.2". Topographic Map (Estimated UTM): Topographic maps have a grid of blue lines known as Universal Transverse Mercator (UTM) coordinates (see Figure 10). The grid lines are spaced every 2 cm in north-south and east-west directions. On 1:50,000 scale maps, this 2-cm spacing equals 1 km on the ground, and 1 mm equals 50 m on the ground. If the distance between any two points on the map is measured, then you can estimate the actual distance on the ground. SHOREKEEPERS GUIDE - MODULE 1 APRIL

17 Note: If you use a topographic map or hydrographic chart to estimate UTM coordinates you must record the map number. To estimate the location of your study area, record the UTM coordinates for the reference point by doing the following. You will need to record an Easting value and a Northing value for the point. The example used to illustrate the procedure is based on estimating the location of point 1 in Figure 10. Locations estimated using this method are accurate to within 50 m on the ground. Determine the six-digit Easting value for the point: Record the number of the closest grid line to the left of the point. Numbers are given at the top and bottom of the map sheet. In this example the number is To this value, add the number of metres represented by the distance between the grid line and the point. Example: The point is located 6 mm to the right of the line, which equals 6 x 50 = 300 m. The Easting value is therefore Determine the seven-digit Northing value for each point: Record the number of the blue grid line immediately below each point. These numbers are given on the left and right margins of the map sheet. In this example the number is To this value add the number of metres represented by the distance between the grid line and the point. Example: The point is located 10 mm above the line, which equals 10 x 50 = 500 m. The Northing value is therefore Example: The study area marked on the map in Figure 10 is 7 mm long, which translates into 350 m at the actual site. The UTM coordinates for the sample point is E , N

18 Figure 9. Example of a Study Area Marked on a Hydrographic Chart. SHOREKEEPERS GUIDE - MODULE 1 APRIL

19 Figure 10. Example a Study Area Marked on a Topographic Map. 66